On Sunday morning, the Moon will reach its perigee (closest approach to Earth) when it is about 357 000km from the Earth.
“The Moon will make its closest approach to the Earth (at perigee) for the year in May. It will happen early morning on Sunday 6th May at about 05:33 and at this time the Moon will be 357 000km from the Earth,” SAAO astronomer Dr Nicola Loaring told News24.
To observers on the ground, the apparent diameter of the Moon will appear the largest for 2012 on 6 May and astronomers believe that there may be some tidal effects due to the Moon, but it may not be noticeable to casual observers.
“The full Moon will have an angular size of 33.7 arc min at this time and is referred to as a perigee full Moon. This coincidence, whereby the full Moon occurs at the same time as the Moon’s closest approach in its orbit happens roughly every 18 years,” said Loaring.
According to information from the SAAO website, the Moon will next be as close to Earth on 23 June 2013.
Full Moons are generally associated with spring tides because of the combined gravitational pull from the Moon and Sun, but in larger bodies, gravity can result in significant heating because of tidal forces.
Astronomers say that this is the reason that Jupiter’s moon Io is an active body. The friction generated by the tidal force between itself and the parent planet results in a heating of its core that results in volcanoes on the surface.
“The closeness of the Moon on the 6th May will have a slight effect on tides around the world. It will result in extra-high ‘perigean tides’.
“However, in most places the tides will only be a few centimetres higher than usual. Local geography can amplify the effect to about 15cm, so no great floods or natural disasters [are expected],” Loaring added.
The weather outlook for Sunday is clear over Johannesburg and Cape Town, so sky watchers in those cities should have a good viewing experience.